Skip update if record does not have hhmemb value

app/services/imports/lettings_logs_field_import_service.rb

@@ -309,6 +309,8 @@ module Imports
       record = LettingsLog.find_by(old_id:)
 
       return @logger.warn("lettings log with old id #{old_id} not found") unless record
+      return @logger.info("lettings log #{record.id} has no hhmemb, skipping update") unless record.hhmemb
+
       if (2..record.hhmemb).all? { |person_index| record.has_any_person_details?(person_index) || record["details_known_#{person_index}"] == 1 }
         return @logger.info("lettings log #{record.id} has all household member details, skipping update")
       end

spec/services/imports/lettings_logs_field_import_service_spec.rb

@@ -1337,5 +1337,20 @@ RSpec.describe Imports::LettingsLogsFieldImportService do
         expect(lettings_log.values_updated_at).to be_nil
       end
     end
+
+    context "when the record has no hhmemb" do
+      let(:lettings_log) { LettingsLog.find_by(old_id: lettings_log_id) }
+
+      before do
+        lettings_log.update!(hhmemb: nil)
+      end
+
+      it "does not update the lettings_log person details" do
+        expect(logger).to receive(:info).with(/lettings log \d+ has no hhmemb, skipping update/)
+        import_service.send(:update_person_details, lettings_log_xml)
+        lettings_log.reload
+        expect(lettings_log.values_updated_at).to be_nil
+      end
+    end
   end
 end